My invention comprises a process to treat contaminated materials, like those found in river sediments, that contain various hazardous contaminates such as coal tar, polychlorinated biphenyls (PCBs), dioxins, furans, pesticides [examples: dichlodiphenytrichloroethane (DDT)], and heavy metals (examples: mercury and lead), and characterized by a high-liquid—low-solids or aqueous content. The proposed continuous or semi-continuous process will destroy, chemically alter, denature and concentrate these typical contaminants into two product (solids) streams. One larger solids stream will have contaminate levels below applicable federal, state, and local guidelines and characterized as non-hazardous, for use as an earthen fill or allow disposal by land spreading. The second, much smaller solids stream, will contain the concentrated heavy metal contaminates (identified as those with high specific gravities). It is anticipated that this solids stream will be transported to a hazardous landfill for disposal.
This process utilizes high pressure and temperature to drive chemical reactions to remove chlorine molecules (a process called dehaloganation), to break some or all of the benzene rings found in these compounds, to partially or totally oxidize carbon compounds, and to otherwise denature, destroy, or chemically alter hazardous organic compounds into non-hazardous states.
The high temperature and pressure process that will be used is similar to that sold by Zimpro Corporation, Rothschild, Wis. (and others) under the name of wet-air oxidation. This standard process allows typical chemical reactions (like oxidation) to take place in an aqueous environment. The wet air oxidation process has been in use for many years. This vendor has attempted to destroy similar contaminate materials (e.g. from the Mississippi River) in pilot lab testing without success using their standard wet air oxidation process. It is believed that the standard wet air oxidation process has been used successfully to destroy pesticides (like DDT).
An alternative process called catalytic wet air oxidation, as promoted by several companies, may be used as part of this treatment process. Testing this process would have to identify a catalyst to help achieve the reactions to break down PCBs. A method for a fixed bed within the reactor or feed of the selected catalyst.
The US Environmental Agency (EPA) has approved chemical dehalogenation as an acceptable process to destroy PCBs in dry soil. The BCD Group, Inc. has patents on their “base catalyzed dehalogenation” (BCD) version of this process. Their two(2)-step process first volatilizes organic compounds from dry soil and then captures these organics from the vapor stream. This first process step is carried out at or near atmospheric pressure at temperatures of about 300° C. (575° F.). In the second process step, the condensed organics are treated in a stirred reactor containing a base, a hydrogen donor compound, and a catalyst like carbon, graphite, or iron. This process requires dry contaminate material to be economically viable per the available literature.
Phase Remediation, Incorporated—a corporation residing in Dartmouth, Nova Scotia, has developed a gravimetric type unit, called the KMS Separator, to separate/concentrate heavy metal materials from “soils and ores primarily” per their literature. This equipment and related process would be modified to concentrate the heavy metal contaminates from my process into a concentrated stream containing only a small percentage of the solids that originally enter the system.
My process incorporates these three processes with other auxiliary equipment and ancillary processes such as dewatering, pollution control, oxygen generation, hydraulic dredging, etc. to treat contaminated sediment like that found in the Fox, Wisconsin and Hudson, New York Rivers (among others), and Duluth/Superior, Wisconsin and Manistique, Michigan Harbors, (among others).
The basis for my process is a continuous/semi-continuous process that uses high pressure and temperature operating conditions to force chemical dehalogenation, oxidation, and other reaction(s) to destroy, denature, or otherwise chemically alter hazardous organic chemicals such as PCBs, dioxins, furans, pesticides, coal tar, etc. in aqueous solutions/slurries/suspensions, into non-hazardous states. Inorganic materials, such as heavy metals characterized by high specific gravities, will be separated/concentrated in subsequent processing steps to remove this type of hazardous material from the process stream.
The process is envisioned to be portable, self-contained, comprehensive, and compact enough to be housed on one or more barges located on the river or other water impoundment containing the contaminated sludge. The process will be connected to a hydraulic dredge that continuously removes the contaminated sludge from the bottom of the body of water for supply to the treatment system (process). This proposed process will offer the following advantages when compared to some or all of the available alternate technologies of hazardous landfilling all removed contaminated sediment/sludge, high temperature incineration, vitrification, off-site treatment, and alternate processes approved and/or tested by the EPA:                Production of a dewatered, non-hazardous material with an economic value as an earthen fill.        Lower transportation costs for sludge removed from the contaminated site since, a majority of the removed material will be classified as non-hazardous and can be transported to any acceptable location that can utilize an earthen fill.        Greatly reduced land acquisition costs adjacent to the river or water impoundment, compared to alternatives since all that is required is a compact land-based site to handle transport of the two solid waste streams, and the supply of consumables and operators to the process. Alternate processes require land-based wastewater treatment plants, sludge dewatering facilities, incinerators, or other sites.        Reduced size and complexity for the hazardous landfill that is required. The volume of material needing hazardous landfilling is <3% of the original solids volume. Heavy metals are not soluble in water, so migration of these contaminants is less likely from a landfill site. (With the major reduction in the volume of material requiring landfilling, there is some possibility that the existing landfills from the area paper mills could be used for this material. This scenario would mean no new landfills would be required.)        The wet air oxidation process drives chemical reactions without the need to first evaporate the water, greatly reducing the heating load for this process.        The standard wet air oxidation process utilizes heat exchanger(s) to efficiently recover a portion of the energy used or generated by oxidation in the process.        Because of the lower operating temperature and enclosed basis for the process, heavy metals will be contained rather than volatilized and potentially lost to the surrounding environment.        The wet air oxidation process is expected to reduce the chemical and biological oxygen demand (COD and BOD) levels in the wastewater streams resulting in simpler, less costly requirements for cleanup before the wastewater is returned to the body of water.        By working with a fixed flowrate, comprehensive process, all equipment can be selected to operate at an efficient level.        